Discussion Forum

A tetrapeptide has a -COOH  group on alanine. This  produces glycine (Gly), valine (Val), phenylalanine (Phe)  and alanine (Ala)  on complete hydrolysis, For this tetrapeptide, the number of possible sequences (primary structures) with -NH₂  group attached  to a chiral center is 

Answer:

Explanation:

Plan A peptide linkage is hydrolysed to two free amino acids.

C'  is a chiral carbon tetrapeptide that has four amino acids joined by three peptide linkage.

-COOH group is on the alanine part, thus it is a fixed C-terminal position in each combination.

Glycine is optically inactive thus it can't be on the N-terminal side.

 Thus, possible combinations are

Phe-Gly-Val-Ala

Phe-Val-Gly-Ala

Val-Gly-Phe-Ala

Val-Phe-Gly-Ala

Thus, in all four possible combinations``